Field
Embodiments of the present invention generally relate to semiconductor substrate processing systems. More specifically, the invention relates to a lid heater assembly for a plasma processing system.
Background
In manufacture of integrated circuits, precise control of various process parameters is required for achieving consistent results within a substrate, as well as the results that are reproducible from substrate to substrate. As the geometry limits of the structures for forming semiconductor devices are pushed against technology limits, tighter tolerances and precise process control are critical to fabrication success. However, with shrinking geometries, precise critical dimension and etch process control has become increasingly difficult.
Many semiconductor devices are processed in the presence of a plasma. If the plasma is not uniformly positioned over the substrate, processing results may also by non-uniform. Various factors may affect plasma uniformity. For example, a heater using electrical means to heat a lid of a plasma chamber during processing may contribute to plasma non-uniformity. Any grounded metallic components in the heater can reduce power transferred from RF power source to the chamber. Electrical heating circuit in the heater can act locally to affect the power transferred into the chamber. Any non-uniformity in heating can increase in deposition and yield undesired particles during processing.
FIG. 1 schematically describes a traditional plasma processing chamber 10 with a heater 13. The plasma processing chamber 10 includes a chamber body defining a processing volume 15 for processing a substrate 12 therein. One or more coils 15, 16 are disposed over a chamber lid 18 of the chamber body 11. The coils 15, 16 ignite and maintain a plasma 17 in the processing volume 15 during processing. A heater 13 including electrically heated element 14 is configured to heat the chamber lid 18 and disposed between the chamber lid 18 and the coils 15, 16. Any metal components of the heater 13 are grounded as with the chamber body 11. The grounded components reduces power transferred from the coils 15, 16 to the plasma 17. The electrically heated element 14 interferences with power transfer between the coils 15, 16 and the plasma 17 because the electrically heated element 14 is positioned in the line-of-sight of the coils 15, 16. Areas of the chamber lid 18 that are closer to the electrically heated element 14 may have a higher temperature, up to 10 degrees Celsius, than areas that are farther from the electrically heated element 14. Temperature non-uniformity of the chamber lid 18 directly affects the uniformity of the plasma 17, which may yield process non-uniformity and particle contamination.
Although conventional plasma processing chambers have proven to be robust performers at larger critical dimensions, existing techniques for controlling the plasma uniformity are one area where improvement in plasma uniformity will contribute to the successful fabrication of next generation, submicron structures, such as those having critical dimensions of about 55 nm and beyond.
The inventors have discovered that improvements to the design of heaters utilized to control the temperature of a lid of the processing chamber have a beneficial effect on plasma uniformity and ignition, and efficient coupling of RF power.